Method for inhibiting fouling in vapor transport system

ABSTRACT

Elimination and/or mitigation of fouling in a vapor transport systems, such as vent lines and scrubber feed lines may be accomplished using an antifouling additive. The method for employing the antifouling additive includes introducing into the vapor transport system an additive including a polar solvent and corrosion inhibitor wherein: the vapor transport system is substantially water free; the vapor transport system is used to transport acidic materials; the additive is a liquid at vapor transport system operating conditions; and the additive is stable at the vapor transport system operating conditions.

CROSS-REFERENCE TO RELATED APPLICATIONS

This applications is a continuation application and claims priority fromU.S. patent Ser. No. 13/920,848 filed on Jun. 18, 2013; which was adivisional application and claimed priority from U.S. Pat. No. 8,465,640filed on Jun. 27, 2011; which claimed the priority from U.S. ProvisionalPatent Application Ser. No. 61/363,928 filed on Jul. 13, 2010; all ofwhich are incorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a method for inhibiting fouling in vaportransport systems. The invention particularly relates to the use ofadditives for inhibiting fouling in vapor transport systems.

2. Background of the Art

Acidic materials may be difficult to use in the manufacture of chemicalsand other products. Unless kept anhydrous, these materials may be verycorrosive and thus requiring the use of exotic, fragile, and/or veryexpensive materials in the construction of units employing them. Forexample, anhydrous HCl is relatively non-corrosive, but introduce even asmall amount of water or other compound that can form a hydronium ion,or its analog, and use of glass lined pipe may be required for safehandling.

This problem is not limited to literal acids, but also extends tocompounds that can generate acids. One example of this is anhydrides.Unsaturated anhydrides are common components of, for example,copolymers. In an anhydrous environment, these compounds arecomparatively stable and non-corrosive. In the presence of waterhowever, they are quickly converted to acids and may be very corrosive.

It is often desirable to handle these compounds as vapor. One problemwith handling these vapors is that solids may form and be deposited onthe surfaces of the systems used to transport the vapor. If notcorrected, this can result in plugging. The foulants are often removedmechanically which may cause substantial losses of productivity.

Care should be employed that solutions to problems within a vaportransport system not cause new problems downstream. For example, in manyprocesses utilizing a vapor transport system it may be desirable toscrub the vapor stream. Gas/Vapor Scrubbers are devices used forseparating components of a gas admixture. In some embodiments, thesedevices are used to “purify” gasses/vapors or, stated in thealternative, remove undesirable components from a gas/vapor stream. Forexample, primitive scrubbers have been used since the inception ofsubmarine warfare to remove carbon dioxide from the air supply in thesubmarine.

More recently, gas scrubbers have proven to be essential in manyindustries. For example, Gas Scrubbers are used to prevent pollutionfrom the burning of coal during power generation. Gas Scrubbers are alsoused to remove undesirable components from process gas streams duringthe production of chemicals, metals and devices such as semiconductorsand the like.

Care should be taken to avoid solutions to plugging problems in a vaportransport system that will result in problems with downstream scrubbers.

SUMMARY OF THE INVENTION

In one aspect, the invention is a method for the prevention ormitigation of fouling in vapor transport systems comprising introducinginto the vapor transport system an additive comprising a polar solventand corrosion inhibitor wherein: the vapor transport system issubstantially water free; the vapor transport system is used totransport acidic materials; the additive is a liquid at vapor transportsystem operating conditions; and the additive is stable at the vaportransport system operating conditions.

In another aspect, the invention is a method for the production ofchemical compositions comprising transporting anhydrous vapor throughmetal pipes and introducing therein an additive comprising a polarsolvent and corrosion inhibitor wherein: the vapor transport system issubstantially water free; the vapor transport system is used totransport acidic materials; the additive is a liquid at vapor transportsystem operating conditions; and the additive is stable at the vaportransport system operating conditions.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

One embodiment of the invention is a method for the prevention ormitigation of fouling in vapor transport systems comprising introducinginto a vapor transport system an additive comprising a polar solvent andcorrosion inhibitor. Examples of polar solvent useful with the methodsof the application may include, but are not limited to: aliphaticalcohols, aliphatic amides and lactams, aliphatic ethers, andcombinations thereof. When the polar solvent is an aliphatic alcohol, insome embodiments it may have from 2 to 14 carbons. In some embodimentsthe aliphatic alcohols may be selected from the group consisting ofethanol, n-propanol, isopropanol, n-butanol, tert-butanol, isobutanol,and mixtures thereof. In other embodiments, especially highertemperature applications, the aliphatic alcohol may be selected from thegroup consisting of n-pentanol, n-hexanol, n-heptanol, n-octanol,n-decanol, n-dodecanol (lauryl alcohol), 2-ethylhexanol, stearylalcohol, cetyl alcohol, lauryl alcohol, cyclopentanol, cyclohexanol,cyclooctanol, cyclododecanol, and combinations thereof. Any aliphaticalcohol which is liquid and stable at the conditions within the vaportransport system may be used with the methods of the disclosure.

When the polar solvent is an aliphatic amide, in some embodiments, itmay be selected from the group consisting of maleic amides, fumaricamides, itaconic amides, citraconic amides and acrylamides. In someembodiments, the aliphatic amide may be N, N-dimethylacrylamide and inother embodiments, it may be N-isopropylacrylamide or N-methacrylamide.In still other embodiments, the aliphatic amide may beN,N-diethylacrylamide. When a lactam is used, the lactam may beN-methyl-2-pyrrolidone. Any aliphatic amide which is liquid and stableat the conditions within the vapor transport system may be used with themethods of the disclosure.

When the polar solvent is an aliphatic ether, in some embodiments, itmay be selected from the group consisting of diethyl ether, diisopropylether and t-butylmethyl ether combinations thereof. In otherembodiments, the aliphatic either may be selected from the groupconsisting of n-propyl ether, n-butyl ether, n-amyl ether, isobutylether, isoamyl and ether and methyl butyl ether. Any aliphatic etherwhich is liquid and stable at the conditions within the vapor transportsystem may be used with the methods of the disclosure.

Polar solvents having both ether and alcohol functionalities may also beused. For example, in some embodiments of the disclosure, ethyleneglycol butyl ether may also be used as the polar solvent.

Corrosion inhibitors that may be used with the methods of the disclosureinclude, but are not limited to, imidazoles and their derivatives,quaternary amines, acetylenic alcohols, pyrimidines, pyridazines,amides, carbamates, and their derivatives and combinations thereof. Whenthe corrosion inhibitor is an imidazole, in some embodiments, it may beselected from the group consisting of benzimidazole, benzothiazole,bifonazole, butaconazole nitrate, clotrimazole, croconazole,eberconazole, econazole, elubiol, fenticonazole, fluconazole,flutimazole, isoconazole, lanoconazole, metronidazole, miconazole,neticonazole, omoconazole, oxiconazole nitrate, sertaconazole,sulconazole nitrate, tioconazole, thiazoles, and triazoles such asterconazole and itraconazole, and mixtures thereof. In otherembodiments, the imidazoles may be selected from the group consisting of1-benzyl-2-methylimidazole, 2-methylimidazole and 2-butylimidazole.

Imidazole derivatives that may be used with the methods of thedisclosure include any aliphatic substituted imidazole. Any imidazolesor imidazole derivatives that are liquid at the operating conditions ofthe vapor transport system may be used.

When the corrosion inhibitor is a quaternary amine, it may be selectedfrom the group consisting of quaternary ammonium compounds andquaternary amines having from about 2 to about 30 carbons. Exemplaryquaternary amines useful with the method of the application include, butare not limited to, quaternized alkylpyridines, quaternized fattyamines. Any quaternary amine which is liquid and stable at theconditions within the vapor transport system may be used with themethods of the disclosure.

When the corrosion inhibitor is an acetylenic alcohol, the acetylenicalcohol may be selected from the group consisting of such alcoholshaving from about 3-16 carbon atoms. In some embodiments, ethyl octynol,propargyl alcohol, hexynol may be used as the corrosion inhibitor. Inother embodiments, methyl butynol, methyl pentynol, hexynol, ethyloctynol, propargyl alcohol, benzyl butynol, naphthalyl butynol, and thelike may be used. Any acetylenic alcohol which is liquid and stable atthe conditions within the vapor transport system may be used with themethods of the disclosure.

When the corrosion inhibitor is a pyrimidine, it may be substituted orunsubstituted. When substituted, is some applications, it may besubstituted with oleic, naphthenic, or fatty type alkyl groups. Forexample, coco or tall oil alkyl groups. Amides and carbamates may besimilarly substituted. In some embodiments, these compounds may havemore than a single substitution.

The corrosion inhibitors useful with some embodiments of the disclosuremay have more than one functional group. For example, in someembodiments, the corrosion inhibitor may have both imidazole and amidefunctionality. In other embodiments, the corrosion inhibitor may haveother combinations. Any polyfunctional corrosion inhibitor known tothose of ordinary skill in the art may be used with the method of theapplication.

In the methods of the disclosure, the vapor transport system issubstantially water free. For the purposes of this application, the term“substantially water free” means that the vapor being transported withinthe vapor transport system has less than 2000 ppm of condensed waterpresent.

The additives of the application have at least two components, a polarsolvent and a corrosion inhibitor. These compounds are present in aratio to each other of from about 1:99 to about 99:1 in some embodimentsand from about 1:9 to about 9:1 in other embodiments. When othercomponents are present, such as a foulant morphology modifier, theconcentration of the polar solvent and corrosion inhibitor may be fromabout 1% to about 99%.

In the practice of the invention, the vapor transport system is used totransport acidic materials. For the purposes of this application, theterm “acidic materials” means compounds capable of forming sufficienthydronium ions in the presence of electrolyte to be corrosive to mostmild steel. In some applications, the acidic materials will be thesource of fouling. For example, where a copolymer is being prepared withmaleic anhydride and the maleic anhydride is plugging a vapor recoverysystem, maleic acid and anhydride is both the foulant and the acidmaterial transported within the vapor transport system.

In contrast, where butene is being transported with an acid materialsuch as anhydrous HCl, and the butene is polymerizing to producepolybutene which is fouling the system, then the HCl is the acidmaterial, but in this embodiment, the polybutene is the foulant.

As already stated, HCl; butene, and maleic anhydride may be componentswithin a vapor transport system as practiced by the methods of theapplication. Other components that may also be used with the methods ofthe application include, but are not limited to 2,5-furandione, phthalicanhydride, and the like.

In the methods of the application, the additive is a liquid at vaportransport system operating conditions. For the purposes of theapplication, this means that the additive, when added to the vaportransport system, is a liquid and below its boiling point although, likeany liquid, the additive may have a vapor pressure and evaporate overtime.

The additives useful with the methods of the applications are stable atthe vapor transport system operating conditions. In the practice ofthese methods, the additive does not decompose and remains effectivefor, in some embodiments, at least 24 hours under the conditions of thevapor transport system. Since conditions will vary depending upon theapplication being served by the vapor transport system, an operator ofsuch a system will well know how to specify/select the additive thatmeets the needs of his particular application. For example, a hightemperature application will require a polar solvent and corrosioninhibitor that have a boiling point greater than the operationaltemperature of the system. In addition to temperature, other conditionsthat may be present in the vapor transport system (and in someembodiments controllable by an operator thereof) include pressure, vaporflow rates, and the selection of components present in the vapor beingtransported.

While not wishing to be bound by any theory, it is never-the-lessbelieved that employing a polar solvent in an acidic vapor transportsystem, while effective at reducing fouling, will result in corrosiondue to the interaction of the acidic materials and the solvent and anylatent water that may be present in the solvent. This is, of course,undesirable. The synergistic combination of the polar solvent and thecorrosion inhibitor allow for the prevention or mitigation of foulingwithout excessive corrosion within the system.

In addition to the other properties, the additives used with the methodsof the disclosure do not act as surfactants or otherwise cause scrubberfailures. Scrubber failures may have safety and environmentalconsequences. At the very least they can cause loss of productivity.

The additives of the application are desirably introduced into the vaportransport systems at an effective concentration. Those of ordinary skillin the art of running such units are well versed in determining theeffective concentration of additives to use in their equipment. Suchconcentrations are dictated by the operational conditions of theequipment. For example in some application, the additives are introducedat a rate of 5000 ppm. In other applications, the additives areintroduced at a rate of 50 ppm.

The additives of the application may be introduced into vapor transportsystems using any process known to be useful to those of ordinary skillin the art of running such systems. Methods of application may includeonline cleanup of existing deposition material via intermittent additiveinjection, and prevention of deposition via continuous additiveinjection.

In addition to the additive components already described, the additivesof the disclosure may include other compounds known to be useful. Anycompound that does not have an undesirable interaction with theadditive's ability to prevent fouling may be used with at least someembodiment of the method of the invention.

Current solutions to the deposition problem include the use ofmechanical cleaning that requires process shutdown limiting plantproduction capacity. Application of the additive may reduce or eliminatemechanical cleaning, system down time, and permit increased operationalutilization thus increasing production capacity.

EXAMPLES

The following examples are provided to illustrate the present invention.The examples are not intended to limit the scope of the presentinvention and they should not be so interpreted. Amounts are in weightparts or weight percentages unless otherwise indicated.

Example 1

74 parts N-methyl-2-pyrrolidone, 20 parts ethylene glycol butyl ether, 3parts alkylated succinic acid, and 3 parts heavy aromatic solvent areadmixed to form a solution. Lab testing was conducted by adding atypical vent line deposit sample composed of poly-butene and2,5-furandione and their derivatives, into the additive at a weightratio of one part deposit per ten parts of additive. A test vialcontaining the mixture was kept isothermal in a water bath heated to170° F. No agitation was applied to the mixture. Within 30 minutes, thedeposit was completely disintegrated, converted into “flow-able” formand suspended in the bulk additive phase.

The same test was repeated in a mixture of the additive and concentratedhydrochloric acid (˜37%) to evaluate the performance in presence ofhydrogen chloride. Within 30 minutes, the deposit was completelydissolved. This test confirmed the efficacy of the additive in acidicenvironment.

Emulsifying tendency of the additive formulation in saturatedhydrochloric acid was also tested. No emulsion formation was observed inthe test.

Example 2

The corrosion potential of the additive formulations on Monel 400metallurgy in presence of anhydrous hydrogen chloride was determined.The testing procedure included purging HCl (g) through the test liquidto saturation, suspending a Monel 400 coupon into the test liquid,sealing the test sample container and settling it at 170° F. for anextended period of time. The corrosion rate is calculated based onweight loss of the coupon through the test due to corrosion. Without aneffective corrosion inhibitor, the corrosion rate of the additiveformulation was 84 MPY on Monel 400. With an effective corrosioninhibitor formulated into the additive, the corrosion rate was tested tobe 17 MPY, an 80% reduction.

1. A method for the prevention or mitigation of fouling in vaportransport systems comprising introducing into the vapor transport systeman additive comprising a polar solvent and corrosion inhibitor wherein:the vapor transport system is substantially water free; the vaportransport system is used to transport at least one acidic material; theadditive is a liquid at vapor transport system operating conditions; theadditive is stable at the vapor transport system operating conditions;and wherein the polar solvent is an aliphatic ether selected from thegroup an aliphatic ether selected from the group consisting of diethylether, diisopropyl ether, t-butylmethyl ether, n-propyl ether, n-butylether, n-amyl ether, isobutyl ether, isoamyl ether, methyl butyl etherand combinations thereof.
 2. The method of claim 1, wherein the at leastone acidic material is also a source of fouling.
 3. The method of claim1, wherein the additive is introduced into the vapor transport systemcontinuously.
 4. The method of claim 3, wherein the continuousintroduction of the additive functions to prevent or mitigate depositionof fouling deposits.
 5. The method of claim 1, wherein the additive isintroduced into the vapor transport system intermittently.
 6. The methodof claim 5, wherein the intermittent introduction of the additivefunctions to at least partially remove existing fouling deposits.
 7. Amethod for the prevention or mitigation of fouling in vapor transportsystems comprising introducing into the vapor transport system anadditive comprising a polar solvent and corrosion inhibitor wherein: thevapor transport system is substantially water free; the vapor transportsystem is used to transport at least one acidic material; the additiveis a liquid at vapor transport system operating conditions; the additiveis stable at the vapor transport system operating conditions; andwherein the corrosion inhibitor is an acetylenic alcohol selected fromthe group consisting of ethyl octynol, propargyl alcohol, hexynol,methyl butynol, methyl pentynol, hexynol, ethyl octynol, propargylalcohol, benzyl butynol, naphthalyl butynol and combinations thereof. 8.The method of claim 7, wherein the at least one acidic material is alsoa source of fouling.
 9. The method of claim 7, wherein the additive isintroduced into the vapor transport system continuously.
 10. The methodof claim 9, wherein the continuous introduction of the additivefunctions to prevent or mitigate deposition of fouling deposits.
 11. Themethod of claim 7, wherein the additive is introduced into the vaportransport system intermittently.
 12. The method of claim 11, wherein theintermittent introduction of the additive functions to at leastpartially remove existing fouling deposits.
 13. A method for theprevention or mitigation of fouling in vapor transport systemscomprising introducing into the vapor transport system an additivecomprising a polar solvent and corrosion inhibitor wherein: the vaportransport system is substantially water free; the vapor transport systemis used to transport at least one acidic material; the additive is aliquid at vapor transport system operating conditions; the additive isstable at the vapor transport system operating conditions; wherein thepolar solvent is an aliphatic ether selected from the group an aliphaticether selected from the group consisting of diethyl ether, diisopropylether, t-butylmethyl ether, n-propyl ether, n-butyl ether, n-amyl ether,isobutyl ether, isoamyl ether, methyl butyl ether and combinationsthereof; and wherein the corrosion inhibitor is an acetylenic alcoholselected from the group consisting of ethyl octynol, propargyl alcohol,hexynol, methyl butynol, methyl pentynol, hexynol, ethyl octynol,propargyl alcohol, benzyl butynol, naphthalyl butynol and combinationsthereof.
 14. The method of claim 13, wherein the at least one acidicmaterial is also a source of fouling.
 15. The method of claim 13,wherein the additive is introduced into the vapor transport systemcontinuously.
 16. The method of claim 15, wherein the continuousintroduction of the additive functions to prevent or mitigate depositionof fouling deposits.
 17. The method of claim 13, wherein the additive isintroduced into the vapor transport system intermittently.
 18. Themethod of claim 17, wherein the intermittent introduction of theadditive functions to at least partially remove existing foulingdeposits.